Antenna device and communication terminal apparatus

ABSTRACT

An antenna device that includes a coil antenna with a coil conductor wound around a winding axis. The device further includes a planar conductor with a surface and an edge end portion, where the surface extends in the direction of the winding axis and the edge end portion is adjacent to a coil opening of the coil conductor. A booster antenna is also provided and includes a looped or spiral coil conductor and is coupled to the planar conductor and/or the coil antenna.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/729,377, filed Dec. 28, 2012, which is a continuation ofInternational application No. PCT/JP2011/070099, filed Sep. 5, 2011,which claims priority to Japanese Patent Application No. 2010-200237,filed Sep. 7, 2010, Japanese Patent Application No. 2010-200966, filedSep. 8, 2010, and Japanese Patent Application No. 2011-010459, filedJan. 21, 2011, the entire contents of each of which are incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to an antenna device and a communicationterminal apparatus and, in particular, to an antenna device and acommunication terminal apparatus used in a communication system in thehigh-frequency (HF) range.

BACKGROUND OF THE INVENTION

A radio frequency identification (RFID) system for exchanginginformation between a reader/writer and an RFID tag by non-contactcommunications is known. Each of the reader/writer and the RFID tagincludes an antenna device for transmitting and receiving a radiosignal. For example, for an HF-range RFID system that uses 13.56 MHz asthe communication frequency, the antenna device of an RFID tag and theantenna device of a reader/writer are coupled to each other mainlythrough an induction field and transmit and receive predeterminedinformation.

In recent years, some communication terminal apparatuses, such ascellular phones, have introduced an RFID system, and the communicationterminal apparatuses have been used as a reader/writer and an RFID tag.As a technique for providing a communication terminal apparatus with theRFID function, as described in, for example, Patent Literature 1, atechnique for incorporating an antenna module in the communicationterminal apparatus is known. The antenna module is one in which a planarcoil antenna is disposed on a planar substrate.

PTL 1: Japanese Unexamined Patent Application Publication No.2004-364199

SUMMARY OF THE INVENTION

In a system that uses the HF range as the communication frequency, thecommunication distance between the antenna devices depends on a magneticflux flowing through the coil antennas. That is, to have a certaindegree of communication distance between the antenna devices, it isnecessary for the coil antennas to have an increased size. The increasedsize of the coil antenna impedes miniaturization of the communicationterminal apparatus.

In light of the above-described circumstances, it is an object of thepresent invention to provide an antenna device that occupies a smallarea while achieving a predetermined communication distance and,additionally, to provide a small communication terminal apparatus.

Solution to Problem

An antenna device according to the present invention includes a coilantenna that includes a coil conductor wound around a winding axis and aplanar conductor (booster antenna) that includes a surface and an edgeend portion, the surface extending along the winding axis, the edge endportion being adjacent (close) to a coil opening of the coil conductor.

A communication terminal apparatus according to the present inventionincludes an antenna device and a communication circuit connected to theantenna device, the antenna device including a coil antenna thatincludes a coil conductor wound around a winding axis and a planarconductor (booster antenna) that includes a surface and an edge endportion, the surface extending along the winding axis, the edge endportion being adjacent (close) to a coil opening of the coil conductor.

Because an antenna device of the present invention includes a coilantenna and a planar conductor, the antenna device occupying a smallarea while ensuring a predetermined communication distance can beachieved and therefore a small communication terminal apparatus can beachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(A) is a perspective view according to an antenna device 201 of afirst embodiment and FIG. 1(B) is a plan view thereof.

FIG. 2 is a perspective view of a coil antenna for use in the antennadevice according to the first embodiment.

FIG. 3 is a perspective view of a communication terminal apparatus thatuses the antenna device according to the first embodiment, theperspective view illustrating an inside portion of the communicationterminal apparatus in use.

FIG. 4 illustrates a relation between the winding axis directions ofcoil conductors of the coil antennas and a planar conductor 11.

FIG. 5(A) illustrates a relation between currents that flow throughcoils L1 to L4 and a current that flows through the planar conductor 11and FIG. 5(B) illustrates a linkage state to coil antennas 100A, 100B,100C, and 100D.

FIG. 6 illustrates a connection relation between coil antennas of anantenna device 202 according to a second embodiment and a connectionrelation with a feed circuit.

FIG. 7(A) is a perspective view of an antenna device 203 according to athird embodiment and FIG. 7(B) is a plan view thereof.

FIG. 8(A) is a perspective view of an antenna device 204 according to afourth embodiment, FIG. 8(B) is a plan view thereof, and FIG. 8(C) is aplan view that illustrates a state where the antenna device 204 isembedded in a communication terminal apparatus, FIG. 8(d) is across-sectional view thereof.

FIG. 9(A) is a perspective view of an antenna device 205 according to afifth embodiment and FIG. 9(B) is a front view that illustrates a statewhere the antenna device 205 is embedded in a communication terminalapparatus.

FIG. 10(A) is a perspective view of an antenna device 206 according to asixth embodiment and FIG. 10(B) is an exploded perspective view thereof.

FIG. 11(A) is a plan view of an antenna device 207 according to aseventh embodiment and FIG. 11(B) illustrates a relation between windingaxis directions of coil conductors of coil antennas and the planarconductor 11.

FIGS. 12(A) and 12(B) are plan views of antenna devices 208A and 208Baccording to an eighth embodiment, respectively.

FIGS. 13(A) and 13(B) are plan views of antenna devices 209A and 209Baccording to a ninth embodiment, respectively.

FIG. 14(A) is a perspective view of an antenna device 210 according to atenth embodiment, FIG. 14(B) is a plan view thereof, and FIG. 14(C) is afront view thereof.

FIG. 15(A) is a perspective view that illustrates a direction of each ofa current that flows through a coil conductor of a coil antenna 100 inthe antenna device 210, a current that flows through the planarconductor 11, a magnetic field produced by the coil antenna 100, and amagnetic field produced by the planar conductor 11. FIG. 15(B)illustrates a relation between a current that flows through the planarconductor 11 and a magnetic flux that occurs.

FIG. 16(A) is a cross-sectional view of a communication terminalapparatus 310 including the antenna device 210 and FIG. 16(B)illustrates an inside portion thereof seen from below.

FIG. 17(A) is a plan view of an antenna device 211 according to an 11thembodiment and FIG. 17(B) is a front view thereof. FIG. 17(C)illustrates is an equivalent circuit diagram of the coil conductor ofthe coil antenna.

FIG. 18 is an exploded perspective view of an antenna device 212according to a 12th embodiment.

FIG. 19(A) is a perspective view of an antenna device 213 according to a13th embodiment and FIG. 19(B) is a cross-sectional view thereof.

FIG. 20(A) is an exploded perspective view of the antenna device 213,and FIG. 20(B) is a cross-sectional view thereof and illustratesbehavior of a current and a magnetic flux.

FIG. 21(A) is an exploded perspective view of a coil antenna 114included in an antenna device according to a 14th embodiment and FIG.21(B) is a cross-sectional view of the antenna device 214 according tothe 14th embodiment.

FIG. 22 is a perspective view that illustrates an inside portion of acommunication terminal apparatus 315 according to a 15th embodiment.

FIG. 23(A) is a perspective view of an antenna device 216 according to a16th embodiment and FIG. 23(B) is a perspective view that illustrates aninside portion of a communication terminal apparatus 316 including theantenna device 216.

FIG. 24 is a perspective view of an antenna device 217 according to a17th embodiment.

FIG. 25(A) is an exploded perspective view of a booster antenna 130included in the antenna device 217 and FIG. 25(B) is an equivalentcircuit diagram thereof. FIG. 25(C) is an equivalent circuit diagram ofthe antenna device 217.

FIG. 26(A) is a plan view of the antenna device 217 and FIG. 26(B) is across-sectional view of a communication terminal apparatus including theantenna device 217.

FIG. 27(A) is a plan view of an antenna device 218 according to an 18thembodiment and FIG. 27(B) is a cross-sectional view of a communicationterminal apparatus including the antenna device 218.

FIG. 28 is a plan view that illustrates a communication terminalapparatus including an antenna device 219 according to a 19th embodimentin a state where the upper housing is detached.

FIG. 29(A) is a plan view of an antenna device 220 and FIG. 29(B) is across-sectional view of the antenna device 220.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An antenna device and a communication terminal apparatus according toembodiments described below are used in an RFID system in the HF range,such as near field communication (NFC).

First Embodiment

FIG. 1(A) is a perspective view of an antenna device 201 according to afirst embodiment and FIG. 1(B) is a plan view thereof.

As illustrated in FIGS. 1(A) and 1(B), the antenna device 201 includesfour coil antennas 100A, 100B, 100C, and 100D. Each of the coil antennas100A, 100B, 100C, and 100D has a structure in which a coil conductor iswound around a magnetic core, as described below.

The antenna device 201 further includes a planar conductor 11 includinga surface parallel to the winding axis direction of each of the coilconductors. The planar conductor 11 is disposed on a base 10. The coilantennas 100A, 100B, 100C, and 100D are mounted on the base 10. Each ofthe coil antennas 100A, 100B, 100C, and 100D is arranged such that acoil opening of the coil conductor is adjacent (close) to the edge endportion of the planar conductor 11.

The planar conductor is made of metallic foil of copper, silver,aluminum, or other metal and is disposed on the base made of flexibleresin.

As illustrated in FIGS. 1(A) and 1(B), each of the coil antennas 100A,100B, 100C, and 100D is arranged such that, when seen from a directionnormal to the planar conductor 11, the end portion of the planarconductor 11 and at least a part of the coil conductor overlap eachother.

FIG. 2 is a perspective view of the coil antenna 100A. The other coilantennas 100B, 100C, and 100D have the same configuration as in the coilantenna 100A, and the coil antenna 100A is described here as arepresentative.

As illustrated in FIG. 2, the coil antenna 100A has a structure in whicha coil conductor 21 made of silver, copper, or other material is woundaround a magnetic core 20 made of, for example, ferrite.

As illustrated in FIG. 2, the coil conductor 21 is wound around theouter surface of the magnetic core 20 such that the winding axis extendsin a direction parallel to the direction of the short sides of themagnetic core 20 having the shape of a rectangular parallelepiped. Thatis, the coil conductor 21 is wound along the longitudinal direction(x-axis direction) of the magnetic core 20. The winding axis and thecoil openings of the coil conductor 21 extend along the transversedirection (y-axis direction). That is, the coil openings of the coilconductor 21 are disposed on the long sides. The coil antenna 100A isconfigured as a so-called surface-mount coil antenna (chip coil antenna)and includes two mounting terminal electrodes (not illustrated) on theback side of the coil antenna. One of the two mounting terminalelectrodes is connected to a first end of the coil conductor 21, and theother is connected to a second end of the coil conductor 21. That is,the coil antenna 100A is surface-mountable on various substrates,including a printed wiring board.

As illustrated in FIG. 1, each of the coil antennas 100A, 100B, 100C,and 100D is arranged such that the coil opening on a first end face sidethereof faces the planar conductor and such that the winding axes of thecoil conductors cross above the region where the planar conductor 11 isformed.

The coil antennas are disposed on the respective sides of the planarconductor 11 having the shape of a rectangle. The coil antennas 100A,100B, 100C, and 100D are arranged so as to surround the planar conductor11. The surface of the planar conductor is overlaid with an insulatingfilm (not illustrated), and the planar conductor 11 and each of the coilantennas 100A, 100B, 100C, and 100D are not directly connected to eachother.

The antenna device 201 can be arranged in a communication terminalapparatus 301, such as a cellular phone, as illustrated in FIG. 3, forexample. That is, in the communication terminal apparatus 301, a mainsubstrate 111 and the base 10 as a sub substrate are incorporated in aterminal housing 320, and the antenna device 201 is configured at thesurface of the base 10. The antenna device 201 and a battery pack 112are arranged in the vicinity of the back surface BS of the terminalhousing 320. The main substrate 111 is a large printed wiring boardincluding a hard resin substrate made of, for example, epoxy resin.Circuit elements forming a driving circuit of a display device, acontrol circuit of the battery, and other circuit are mounted on themain substrate 111. The base 10 as the sub substrate includes a flexibleresin substrate made of a polyimide, a liquid crystal polymer, or otherresin. In addition to the antenna device 201, circuit elements forming acommunication circuit (RF circuit) and other circuit are mounted on thebase 10. When the communication terminal apparatus 301 is held over acoil antenna 400 at the other end in communication, as illustrated inFIG. 3, the antenna device 201 and the coil antenna 400 at the other endin communication are coupled mainly through an induction field andpredetermined information is transmitted and received.

FIG. 4 illustrates a relation between the winding axis direction of thecoil conductor of each of the coil antennas and the planar conductor 11.The coil conductors of the coil antennas are denoted as coils L1 to L4here. As illustrated in FIG. 4, in the antenna device 201 according tothe present embodiment, the coils L1 to L4 are connected in series andconnected to a feed circuit FC. It is preferable that connection wiringW1 between the feed circuit FC and the coil L1, connection wiring W2 toW4 between the coils L1 to L4, connection wiring W5 between the coil L4and the feed circuit FC be arranged outside the area formed by animaginary straight line that connects the center positions of the coilantennas together because the usable area in the planar conductor 11 iswide. In this respect, it is preferable that the connection wiring W1 toW5 be arranged outside the planar conductor 11. The feed circuit FC canbe a radio-frequency integrated circuit (RFIC) including a communicationcircuit and tag information, for example.

FIG. 5(A) illustrates a relation between currents that flow through thecoils L1 to L4 and a current that flows through the planar conductor 11,and FIG. 5(B) illustrates a linkage state to the coil antennas 100A,100B, 100C, and 100D.

When the planar conductor 11 in the antenna device 201 according to thepresent embodiment receives a magnetic field from an antenna device atthe other end in communication, as illustrated in FIG. 5(A), an eddycurrent (induced current) occurs in the planar conductor 11. The eddycurrent also flows in the vicinity of the end edge portion of the planarconductor 11, as indicated by the arrows (of dotted lines) in FIG. 5(A).The magnetic field produced by that current causes a current in adirection opposite to the direction of the current flowing through theend edge portion of the planar conductor 11 to flow through a portion ofeach of the coils L1 to L4, the portion being close to the edge endportion of the planar conductor 11. As a result, currents indicated bythe arrows (of dot-and-dash lines) in FIG. 5(A) also flow through theconnection wiring W1 to W5.

Of a magnetic field from the antenna device at the other end incommunication, a magnetic flux (indicated by the solid lines in FIG.5(B)) other than the component from which the eddy current occurs in theplanar conductor 11 passes through each of the coil antennas 100A, 100B,100C, and 100D, which are arranged on the edge end portion of the planarconductor 11, as illustrated in FIG. 5(B). That is, the magnetic fluxentering each of the coils L1 to L4 illustrated in FIG. 5(A) induces acurrent in the coil conductor, and as a result, the currents flow, asindicated by the arrows (of dot-and-dash lines) in FIG. 5(A). When acurrent is supplied from the feed circuit FC, a phenomenon opposite tothe above occurs. In this manner, the planar conductor 11 acts as abooster antenna.

As described above, according to the present embodiment, the use of aplurality of coil antennas, in particular, a plurality of surface-mountcoil antennas, in addition, the use of a magnetic field coupling betweenthe planar conductor and the coil antennas enables an antenna devicehaving electric characteristics substantially equivalent to or betterthan those of a large coil antenna and can reduce the area occupied bythe coil antennas without the use of a large coil antenna. As a result,the communication terminal apparatus can be miniaturized.

In the foregoing, an example in which the winding axis direction of thecoil conductor of each coil antenna is parallel to the surface of theplanar conductor is illustrated. Being parallel does not necessarilyrequire being strictly parallel and only requires that the surface ofthe planar conductor extend along the winding axis of the coilconductor. In other words, it is only required that the coil antenna bearranged such that the winding axis of the coil conductor extends alongthe planar conductor. For example, when the winding axis direction ofthe coil conductor is in the range from −45° to +45° with respect to adirection normal to the planar conductor 11, this is considered to bethe state of extending “along” in the present invention. The sameapplies to other embodiments described below.

It is only required that the coil conductor 21 of each coil antenna beclose to the end portion of the planar conductor 11. It is preferablethat, when seen from a direction normal to the planar conductor 11, theend portion of the planar conductor 11 and at least a part of the coilconductor 21 overlap each other, as described above because a currentflowing through the end portion of the planar conductor 11 can be moreeasily induced to the coil conductor 21. From the same reason, it ispreferable that a portion in the coil conductor 21, the portion beingclosest to the end portion of the planar conductor 11, extend in adirection parallel to the end portion of the planar conductor 11. It ispreferable that the end portion of the planar conductor 11 and at leasta part of the magnetic core 20 overlap each other because a conductiveportion of the coil conductor 21 in the vicinity of the bottom side ofthe magnetic core 20 and the planar conductor 11 are coupled, whereas aconductive portion in the vicinity of the top side of the magnetic core20 is not easily coupled to the planar conductor 11, and the occurrenceof currents cancelling out each other can be prevented.

It is preferable that each coil antenna be arranged such that thewinding axes of the coil conductors 21 are parallel (coaxial) to eachother because the component of a magnetic flux in the winding axisdirection is cancelled and directivity of the antenna device in adirection normal to the planar conductor 11 is obtained.

It is preferable that each coil antenna be arranged such that thewinding axes of the coil conductors 21 of the coil antennas cross abovethe region where the planar conductor 11 is formed because a magneticflux heading for that intersection can sufficiently flow through eachcoil antenna.

It is preferable that the magnetic core 20 in each of the coil antennashave the shape of a rectangular parallelepiped and that the coilconductor 21 be wound so as to have the winding axis being parallel tothe short sides of the magnetic core 20, that is, the coil conductor 21be wound such that the coil openings are disposed on the long side ofthe magnetic core 20. This is because a current flowing through theplanar conductor 11 can be more easily guided to the coil conductor 21and a magnetic flux flowing in a direction parallel to the planarconductor 11 can more easily flow through the coil antenna without anincrease in the area for disposing the coil antenna.

Additionally, it is preferable that, when seen from a direction normalto the planar conductor 11, the coil conductor 21 be arranged so as toinclude a first portion where it overlaps the end portion of the planarconductor 11 and a second portion where it does not overlap the planarconductor 11. This is because the frequency characteristic does not tendto vary if the coil antenna is misaligned at the time of placement andalso because an eddy current flowing through the planar conductor 11 islarge in the vicinity of the edge end portion of the planar conductor 11and thus the degree of coupling (magnetic coupling) between the planarconductor 11 and the coil conductor 21 can be large, and as a result, anantenna device with a reduced loss can be achieved.

Second Embodiment

FIG. 6 illustrates a connection relation between the coil antennas of anantenna device 202 according to a second embodiment and a connectionrelation with a feed circuit. The coil conductors of the coil antennasare denoted as the coils L1 to L4 here. The configuration of each coilantenna is substantially the same as in the first embodiment.

As illustrated in FIG. 6, in the antenna device 202 according to thepresent embodiment, each of the coils L1 to L4 is connected to the feedcircuit FC. That is, the coil conductors of the coil antennas areconnected to the feed circuit FC such that they are in parallel to eachother. More specifically, a first input/output port of the feed circuitFC is connected to a first end of the coil L1 through wiring W1, and asecond end of the coil L1 is connected to a second input/output port ofthe feed circuit FC through wiring W2. Similarly, the first input/outputport of the feed circuit FC is connected to a first end of the coil L2through wiring W3, and a second end of the coil L2 is connected to thesecond input/output port of the feed circuit FC through wiring W4. Thefirst input/output port of the feed circuit FC is connected to a firstend of the coil L3 through wiring W5, and a second end of the coil L3 isconnected to the second input/output port of the feed circuit FC throughwiring W6. The first input/output port of the feed circuit FC isconnected to a first end of the coil L4 through wiring W7, and a secondend of the coil L4 is connected to the second input/output port of thefeed circuit FC through wiring W8. In this manner, when the coilantennas are connected in parallel to each other, even if the coilinductance values are uneven or any of the coil antennas becomesdefective, the other coil antennas can compensate for that defect.

Also in the present embodiment, each of the wiring W1 to W8 connectingthe coil antennas and the feed circuit FC is routed outside the areaformed by an imaginary straight line that connects the center positionsof the coil antennas (coil L1, coil L2, coil L3, and coil L4) together.Moreover, each of the wiring W1 to W8 is routed outside the planarconductor 11. Routing the wiring W1 to W8 in this manner widens the areausable as the antenna device in the planar conductor 11.

As in the present embodiment, when seen from a direction normal to theplanar conductor 11, the coil antennas (coils L1 to L4) may be arrangedsuch that all of them are located within the area of the planarconductor 11. Because the core of each of the coil antennas is magnetic,currents that cancel out each other do not tend to occur for anyarrangement.

The other configurations, operations, and advantageous effects aresubstantially the same as those of the antenna device according to thefirst embodiment.

Third Embodiment

FIG. 7(A) is a perspective view of an antenna device 203 according to athird embodiment and FIG. 7(B) is a plan view thereof.

As illustrated in FIGS. 7(A) and 7(B), the antenna device 203 accordingto the third embodiment is the one in which the first coil antenna 100Ais arranged in the vicinity of one of the two long sides of therectangular planar conductor 11 and the second coil antenna 100B and thethird coil antenna 100C are arranged in the vicinities of the two shortsides. In this manner, the arrangement in which a plurality of coilantennas are arranged such that the coil openings thereof face eachother in the direction of the long sides of the planar conductor 11enables a magnetic flux to be efficiently guided to the coil antennas.

As illustrated in FIGS. 7(A) and 7(B), the arrangement in which theplurality of coil antennas 100A, 100B, and 100C are asymmetric withrespect to the center of the planar conductor 11 enables the antennadevice 203 to have directivity. Accordingly, for example, arrangement ofthe plurality of coil antennas with respect to the planar conductor 11can be set such that, in a state where the antenna device 203 isembedded in a communication terminal apparatus, the directivitydirection is inclined to the longitudinal direction of the housing.

The coil antennas may be connected in series, or alternatively, may alsobe connected in parallel.

Fourth Embodiment

FIG. 8(A) is a perspective view of an antenna device 204 according to afourth embodiment, and FIG. 8(B) is a plan view thereof. FIG. 8(C) is aplan view that illustrates a state where the antenna device 204 isembedded in a communication terminal apparatus, and FIG. 8(D) is a frontview thereof.

As illustrated in FIGS. 8(A) and 8(B), the antenna device 204 accordingto the present embodiment is the one in which the first coil antenna100A is disposed on one of the four sides of the rectangular planarconductor 11 and the second coil antenna 100B, the third coil antenna100C, and the fourth coil antenna 100D are disposed on the opposed side.In this manner, the arrangement in which the plurality of coil antennas100A, 100B, 100C, and 100D are arranged asymmetric with respect to thecenter of the planar conductor 11 enables the antenna device 204 to havedirectivity. In the present embodiment, the communication distance forthe side on which the second coil antenna 100B, the third coil antenna100C, and the fourth coil antenna 100D are disposed can be increased.

As illustrated in FIGS. 8(C) and 8(D), the antenna device 204 isarranged in a leading end portion of the terminal housing 320 of thecommunication terminal apparatus. That is, arrangement in which theantenna device 204, which is asymmetric to have directivity in theabove-described direction, is positioned at the base 10 (printedsubstrate) such that the side on which the second coil antenna 100B, thethird coil antenna 100C, and the fourth coil antenna 100D are arrangedis situated at the leading end portion of the terminal housing 320enables the communication terminal apparatus to have the illustrateddirectivity.

The coil antennas may be connected in series, or alternatively, may alsobe connected in parallel.

Fifth Embodiment

FIG. 9(A) is a perspective view of an antenna device 205 according to afifth embodiment and FIG. 9(B) is a front view that illustrates a statewhere the antenna device 205 is embedded in a communication terminalapparatus.

As illustrated in FIG. 9(A), the antenna device 205 according to thepresent embodiment includes a first planar conductor region 11A in whichthe first coil antenna 100A, the second coil antenna 100B, and the thirdcoil antenna 100C are arranged and a second planar conductor region 11Bin which the fourth coil antenna 100D is arranged. The first planarconductor region 11A and the second planar conductor region 11B areformed on respective planes that intersect each other at a predeterminedangle θ. In this case, the antenna device has directivity in a directionthat is intermediate between a direction normal to the first planarconductor region 11A and a direction normal to the second planarconductor region 11B and can have an increased communication distance inthat direction.

As illustrated in FIG. 9(B), the antenna device 205 is arranged on afront end FE side of the terminal housing 320 of the communicationterminal apparatus. That is, arrangement in which the antenna device205, which is asymmetric to have directivity in that direction, ispositioned in the vicinity of the back surface BS of the terminalhousing 320 and the second planar conductor region 11B is disposed onthe leading end portion FE side enables the communication terminalapparatus to have the illustrated directivity.

The coil antennas may be connected in series, or alternatively, may alsobe connected in parallel. To prevent an increase in the loss of acurrent flowing through the first planar conductor region 11A and thesecond planar conductor region 11B, it is preferable that the angle θformed between the first planar conductor region 11A and the secondplanar conductor region 11B be larger than 90° and smaller than 135°.

Sixth Embodiment

FIG. 10(A) is a perspective view of an antenna device 206 according to asixth embodiment and FIG. 10(B) is an exploded perspective view thereof.As illustrated in FIGS. 10(A) and 10(B), the antenna device 206 includesa chip coil antenna 106 and the planar conductor 11. The coil antenna106 and the planar conductor 11 are directly connected to each otherwith a conductive binder, such as solder, disposed therebetween.

The coil antenna 106 includes, as a body, a stacked magnetic core inwhich magnetic layers 20 a, 20 c, and 20 b are stacked. A conductivepattern 21 a on the surface of the magnetic layer 20 a, a conductivepattern 21 c on the side surface of each of the magnetic layers 20 a, 20c, and 20 b, and a conductive pattern 21 b on the surface of themagnetic layer 20 b form a coil conductor. Input/output-terminalconnection electrodes 22 a and 22 b for use in connecting toinput/output terminals 12 a and 12 b and a coupling electrode 24 for usein connecting to the planar conductor 11 are disposed on the backsurface of the magnetic layer 20 b, that is, on the mounting surface ofthe coil antenna 106.

The coil conductor is connected at one end to the input/output-terminalconnection electrode 22 a and is connected at the other end to theinput/output-terminal connection electrode 22 b.

The input/output-terminal connection electrodes 22 a and 22 b areconnected and fixed to the input/output terminals 12 a and 12 b with aconductive binder, such as solder, disposed therebetween. The couplingelectrode 24 is connected and fixed to a connection area CA indicated bythe broken lines in FIG. 10(B) with a conductive binder, such as solder,disposed therebetween, the connection area CA being a part of the planarconductor 11.

The input/output terminals 12 a and 12 b are connected to aninput/output port of a feed circuit and another coil antenna.

In the antenna device 206, an eddy current (induced current) flowingthrough the planar conductor 11 is also guided to the coupling electrode24 through the conductive binder because the planar conductor 11 and thecoupling electrode 24 have the same potential. A current flowing in adirection opposite to the direction of the current flowing in thecoupling electrode 24 flows through the conductive pattern 21 b on thesurface of the magnetic layer 20 b, and as a result, the current flowsthrough the coil conductor. In particular, according to the presentembodiment, because the coupling electrode 24 and the coil conductorface each other such that the magnetic layer is disposed therebetween, amagnetic field produced by the current flowing in the coupling electrode24 is trapped in the magnetic layer and is efficiently guided to thecoil conductor. Accordingly, the degree of the magnetic field couplingbetween the coupling electrode 24 and the coil conductor can beincreased, and the antenna device with a reduced loss can be achieved.

Seventh Embodiment

FIG. 11(A) is a plan view of an antenna device 207 according to aseventh embodiment and FIG. 11(B) illustrates a relation between thewinding axis directions of the coil conductors of the coil antennas andthe planar conductor 11. The coil conductors of the coil antennas aredenoted as coils L1 and L2 here.

In the present invention, the number of coil antennas is not limited tothree or more. As illustrated in FIG. 11(A), the two coil antennas 100Aand 100B may be used. Arrangement in which the two coil antennas 100Aand 100B are asymmetric with respect to the center of the planarconductor 11 enables the antenna device 207 to have directivity. Also inthis case, as illustrated in FIG. 11(B), the coil conductors (coils L1and L2) of the two coil antennas may be connected in series, oralternatively, may also be connected in parallel.

An increase in the number of coil antennas facilitates the coilconductors to catch an eddy current occurring in the planar conductor11, but increases the size of the antenna device accordingly. The numberof coil antennas can be determined in consideration of balance betweenthe electric characteristics required for the antenna device and thesize.

Eighth Embodiment

FIGS. 12(A) and 12(B) are plan views of antenna devices 208A and 208Baccording to an eighth embodiment, respectively. In the presentinvention, the shape of the planar conductor 11 is not limited to arectangular. For example, as illustrated in FIG. 12(A), the planarconductor 11 may be circular. Alternatively, as illustrated in FIG.12(B), the planar conductor 11 may be hexagonal. In FIGS. 12(A) and12(B), a coil antenna having substantially the same configuration as anyof the coil antennas described above may be applied to the coil antennas100A, 100B, 100C, and 100D.

Ninth Embodiment

FIGS. 13(A) and 13(B) are plan views of antenna devices 209A and 209Baccording to a ninth embodiment, respectively. In the present invention,the shape of the planar conductor 11 is not limited to a continuousplanar shape. For example, as illustrated in FIG. 13(A), the planarconductor 11 may have an opening A in the central portion, oralternatively, as illustrated in FIG. 13(B), the planar conductor 11 mayhave a slit SL in the vicinity of a coil opening of each of the coilantennas 100A, 100B, 100C, and 100D. These structures allow a magneticflux to exit through the opening A or the slit SL and thus enablecommunication to not only a first main surface side but also a secondmain surface side. Additionally, the total magnetic flux is alsoincreased, and the distance at which communication can be carried out isalso increased.

Tenth Embodiment

FIG. 14(A) is a perspective view of an antenna device 210 according to atenth embodiment, FIG. 14(B) is a plan view thereof, and FIG. 14(C) is afront view thereof.

The base 10 of the antenna device 210 is a printed wiring board. Theplanar conductor 11 is disposed on the base 10. The coil antenna 100includes the magnetic core 20 and the coil conductor 21 wound around themagnetic core 20. The coil antenna 100 is arranged such that a coilopening of the coil conductor is adjacent (close) to the edge endportion of the planar conductor 11.

Here, it is preferable that 0<d1<d2, where d2 is the distance from theinner end face of the magnetic core 20 to the edge end of the planarconductor 11 and d1 is the distance from the inner end portion of thewinding region of the coil conductor to the edge end of the planarconductor 11. When d1 is small or d2 is large, the degree of couplingbetween the coil conductor 21 and the planar conductor 11 is high, thatis, the induced current is increased; as a result, an advantageouseffect of increasing a magnetic flux from the planar conductor 11 isobtainable.

FIG. 15(A) is a perspective view that illustrates a direction of each ofa current that flows through the coil conductor of the coil antenna 100in the antenna device 210, a current that flows through the planarconductor 11, a magnetic field produced by the coil antenna 100, and amagnetic field produced by the planar conductor 11. FIG. 15(B)illustrates a relation between a current that flows through the planarconductor 11 and a magnetic flux produced by the current.

A current “a” flowing through the coil conductor 21 induces a current“b” in the planar conductor 11. As a result, a magnetic field occurs inthe coil antenna 100 in the direction indicated by the arrow A, and amagnetic field occurs in the planar conductor 11 in the directionindicated by the arrow B. When a magnetic flux is introduced from a coilantenna at the other end in communication, a phenomenon opposite to theabove occurs. That is, the planar conductor 11 functions as a boosterantenna, and a magnetic field larger than a magnetic field produced bythe coil antenna 100 alone can be produced. In this example, asillustrated in FIG. 15(B), directivity in the 0° direction and that inthe 45° direction are enhanced.

The reason why the above phenomenon, in which such a large magneticfield can be produced, occurs can be that, when seen from a directionnormal to the planar conductor 11, the direction of a current flowingthrough the coil conductor 21 and the direction of a current circulatingin the edge end of the planar conductor 11 are the same.

FIG. 16(A) is a cross-sectional view of a communication terminalapparatus 310 including the antenna device 210 and FIG. 16(B) is a planview that illustrates an inside portion thereof. As illustrated in FIG.15(A), a magnetic flux produced by the coil antenna 100 and a magneticflux produced by the planar conductor 11 are combined, and the antennadevice 210 has directivity in the direction indicated by the arrowillustrated in FIG. 16(A). That is, arrangement of the coil antenna 100in the antenna device 210 on the end portion side of the terminalhousing 320 enables the antenna device 210 to have a high gain in aninclined direction between the back surface BS direction and the leadingend FE direction of the terminal housing 320 of the communicationterminal apparatus 310. Accordingly, when a user grips a proximalportion HP of the communication terminal apparatus 310 and holds thelower surface side angle of the leading end portion over an object atthe other end in communication, the communication can be carried outwith a high gain.

11th Embodiment

FIG. 17(A) is a plan view of an antenna device 211 according to an 11thembodiment and FIG. 17(B) is a front view thereof. In the antenna device211, the two planar conductors 11A and 11B are disposed inside the base10. The base 10 is a printed wiring board. The coil antenna 100 includesthe magnetic core 20 and the coil conductor 21 wound around the magneticcore 20. Both ends of the coil conductor 21 are not connected to theplanar conductors 11A and 11B, and the planar conductors 11A and 11B arein an insulated state in terms of direct current. The coil conductor 21has a circuit configuration illustrated in FIG. 17(C).

The coil antenna 100 and the planar conductors 11A and 11B are arrangedsuch that the two coil openings of the coil conductor 21 of the coilantenna 100 are adjacent (close) to the edge end portions of the planarconductors 11A and 11B, respectively.

In the structure illustrated in FIGS. 17(A) to 17(C), the direction of acurrent circulating in the edge end of the planar conductor 11A and thatin the edge end of the planar conductor 11B are the same. Thus magneticfields in the planar conductors are mutually strengthened, and thecommunication distance is further increased.

12th Embodiment

FIG. 18 is an exploded perspective view of an antenna device 212according to a 12th embodiment. A base is made of a stacked substrate inwhich base layers 10 a, 10 b, and 10 c are stacked. The conductivepattern 21 a is disposed on the base layer 10 a, and the conductivepattern 21 c is disposed on the base layer 10 c. The base layers 10 a,10 b, and 10 c have via conductors 21 v. The conductive patterns 21 aand 21 c and the via conductors 21 v form a single coil conductor havinga plurality of turns. The input/output-terminal connection electrodes 22a and 22 b are disposed on the lower surface of the base layer 10 c.

The planar conductor 11 is disposed on the base layer 10 a. The planarconductor 11 is disposed such that the edge end portion is adjacent(close) to a coil opening of the coil conductor. In this manner, theantenna device in which the coil antenna and the planar conductor areintegrated in the stacked substrate is configured.

13th Embodiment

FIG. 19(A) is a perspective view of an antenna device 213 according to a13th embodiment and FIG. 19(B) is a cross-sectional view thereof. FIG.20(A) is an exploded perspective view of the antenna device 213, andFIG. 20(B) is a cross-sectional view thereof and illustrates behavior ofa current and a magnetic flux. The antenna device 213 includes a chipcoil antenna 113 and the planar conductor 11. The coil antenna 113 andthe planar conductor 11 are directly connected to each other with aconductive binder cb, such as solder, disposed therebetween.

The coil antenna 113 includes, as a body, a stacked magnetic core inwhich the magnetic layers 20 a, 20 c, and 20 b are stacked. Theconductive pattern 21 a on the surface of the magnetic layer 20 a, theconductive pattern 21 c on the side surface of each of the magneticlayers 20 a, 20 c, and 20 b, and the conductive pattern 21 b on thesurface of the magnetic layer 20 b form a coil conductor.

The input/output-terminal connection electrodes 22 a and 22 b for use inconnecting to the input/output terminals 12 a and 12 b and a stripcoupling electrode 23 are disposed on the back surface of the magneticlayer 20 b, that is, on the mounting surface of the coil antenna 113.The coil conductor is connected at one end to the input/output-terminalconnection electrode 22 a through a via conductor and is connected atthe other end to the input/output-terminal connection electrode 22 bthrough a via conductor.

The input/output-terminal connection electrodes 22 a and 22 b areconnected and fixed to the input/output terminals 12 a and 12 b with aconductive binder, such as solder, disposed therebetween. The couplingelectrode 23 is connected and fixed to the connection area CA indicatedby the broken lines in FIG. 20(A) with a conductive binder, such assolder, disposed therebetween, the connection area CA being a part ofthe planar conductor 11.

The input/output terminals 12 a and 12 b are connected to aninput/output port of a feed circuit and another coil antenna.

In the antenna device 213, an eddy current (induced current) flowingthrough the planar conductor 11 is also guided to the coupling electrode23 through the conductive binder because the planar conductor 11 and thecoupling electrode 23 have the same potential. A current flowing in adirection opposite to the direction of the current flowing in thecoupling electrode 23 flows through the conductive pattern 21 b on thesurface of the magnetic layer 20 b, and as a result, the current flowsthrough the coil conductor. In particular, according to the presentembodiment, because the coupling electrode 23 and the coil conductorface each other such that the magnetic layer is disposed therebetween, amagnetic field produced by the current flowing in the coupling electrode23 is trapped in the magnetic layer and is efficiently guided to thecoil conductor. Accordingly, the degree of the magnetic field couplingbetween the coupling electrode 23 and the coil conductor can beincreased, and the antenna device with a reduced loss can be achieved.

14th Embodiment

FIG. 21(A) is an exploded perspective view of a coil antenna 114included in an antenna device according to a 14th embodiment and FIG.21(B) is a cross-sectional view of the antenna device 214 according tothe 14th embodiment. The antenna device 214 includes the chip coilantenna 114 and the planar conductor 11. The coil antenna 114 and theplanar conductor 11 are directly connected to each other with aconductive binder, such as solder, disposed therebetween.

The coil antenna 114 includes, as a body, a stacked magnetic core inwhich the magnetic layers 20 a, 20 c, 20 b, and 20 d are stacked. Theconductive pattern 21 a on the surface of the magnetic layer 20 a, theconductive pattern 21 c on the side surface of each of the magneticlayers 20 a, 20 c, and 20 b, and the conductive pattern 21 b on thesurface of the magnetic layer 20 b form a coil conductor.

The coupling electrode 23 is disposed on the upper surface of themagnetic layer 20 d. The input/output-terminal connection electrodes 22a and 22 b electrically connected to both ends of the coil conductorthrough via conductors and coupling-electrode connection electrodes 23 aand 23 b electrically connected to both ends of the coupling electrode23 through via conductors are disposed on the back surface of themagnetic layer 20 d, that is, on the mounting surface of the coilantenna 114.

The input/output-terminal connection electrodes 22 a and 22 b areconnected and fixed to the input/output terminals on the base 10 with aconductive binder, such as solder, disposed therebetween. Thecoupling-electrode connection electrodes 23 a and 23 b are connected andfixed to the connection area being a part of the planar conductor 11with a conductive binder, such as solder, disposed therebetween. Anunderfill 25 is disposed on the lower surface of the coil antenna 114.

In the antenna device 214, an eddy current (induced current) flowingthrough the planar conductor 11 is also guided to the coupling electrode23 through the conductive binder. A current flowing in a directionopposite to the direction of the current flowing in the couplingelectrode 23 flows through the conductive pattern 21 b on the surface ofthe magnetic layer 20 b, and as a result, the current flows through thecoil conductor. In particular, according to the present embodiment,because the coupling electrode 23 and the coil conductor face each othersuch that the magnetic layer is disposed therebetween, a magnetic fieldproduced by the current flowing in the coupling electrode 23 is trappedin the magnetic layer and is efficiently guided to the coil conductor.Accordingly, the degree of the magnetic field coupling between thecoupling electrode 23 and the coil conductor can be increased, and theantenna device with a reduced loss can be achieved.

15th Embodiment

FIG. 22 is a perspective view that illustrates an inside portion of acommunication terminal apparatus 315 according to a 15th embodiment. Inthe communication terminal apparatus 315, the main substrate 111 and thebase 10 as a sub substrate are incorporated in the terminal housing 320,and an antenna device 215 is configured at the base 10. The antennadevice 215 includes the planar conductor 11 and two coil antennas 113Aand 113B. Each of the coil antennas 113A and 113B is the one illustratedin FIGS. 19 and 20 in the 13th embodiment. In the example illustrated inFIG. 22, the coil antennas 113A and 113B are arranged on two sections ofthe edge end portion of the planar conductor 11. The antenna device 215and the battery pack 112 are arranged in the vicinity of the backsurface BS of the terminal housing 320.

Because the two coil antennas 113A and 113B of the antenna device 215are opposed to each other, components in the plane direction (horizontaldirection) of the planar conductor 11 of the magnetic fluxes produced bythe coil antennas 113A and 113B are cancelled. Thus directivity of theantenna device 215 has a characteristic in which it is directed to adirection normal to the planar conductor 11.

When the communication terminal apparatus 315 is held over the coilantenna 400 at the other end in communication, as illustrated in FIG.22, the antenna device 215 and the coil antenna 400 at the other end incommunication are coupled mainly through an induction field, andpredetermined information is transmitted and received.

16th Embodiment

FIG. 23(A) is a perspective view of an antenna device 216 according to a16th embodiment and FIG. 23(B) is a perspective view that illustrates aninside portion of a communication terminal apparatus 316 including theantenna device 216.

In the communication terminal apparatus 316, the main substrate 111 andthe base 10 as a sub substrate are incorporated in the terminal housing320. The antenna device 216 is configured at the base 10.

The antenna device 216 includes the planar conductor 11 and the singlecoil antenna 114. The coil antenna 114 is the one illustrated in FIG. 21in the 14th embodiment. The antenna device 216 and the battery pack 112are arranged in the vicinity of the back surface BS of the terminalhousing 320.

The antenna coil 114 is arranged on the edge end portion of the planarconductor 11 inside the leading end portion FE of the terminal housing320, a magnetic flux produced by the coil antenna 114 and a magneticflux produced by the planar conductor 11 are combined, and thus theantenna device 216 has directivity in the direction indicated by thearrow illustrated in FIG. 23(B). That is, the antenna device 216 obtainsa high gain in an inclined direction between the back surface BSdirection and the leading end FE direction of the terminal housing 320of the communication terminal apparatus 316. Accordingly, when a usergrips the proximal portion of the communication terminal apparatus 316and holds the lower surface side angle of the leading end portion overthe coil antenna 400 at the other end in communication, thecommunication can be carried out with a high gain.

17th Embodiment

FIG. 24 is a perspective view of an antenna device 217 according to a17th embodiment.

The antenna device 217 of the 17th embodiment includes a booster antenna(booster coil) 130 coupled to the coil antenna 100. The planar conductor11 is disposed inside the main substrate (printed wiring board) 111. Thecoil opening on a first end face side in the coil antenna 100 faces theplanar conductor 11, and the coil antenna 100 is arranged on the uppersurface of the main substrate 111. The coil antenna 100 has the sameconfiguration as that illustrated in FIG. 2 and other drawings in thefirst embodiment.

The booster antenna 130 is coupled to the coil antenna 100 and a coilantenna at the other end in communication and acts as a booster antenna,as described below. The coil antenna 100 is connected to a feed circuit,and that feed circuit carries out communication through the coil antenna100, the booster antenna 130, and the coil antenna at the other end incommunication.

FIG. 25(A) is an exploded perspective view of the booster antenna 130included in the antenna device 217, and FIG. 25(B) is an equivalentcircuit diagram thereof. FIG. 25(C) is an equivalent circuit diagram ofthe antenna device 217. As illustrated in FIG. 25(A), the boosterantenna 130 includes a base sheet 30, a first coil conductor 31, and asecond coil conductor 32. Each of the coil conductor 31 and the coilconductor 32 is patterned so as to have a rectangular spiral shape. Thewinding direction of the coil conductor 31 and that of the coilconductor 32 are opposite (the same when seen through from onedirection), and both are coupled through an electromagnetic field. InFIG. 25(B), an inductor L31 is the one in which an inductance producedby the coil conductor 31 is indicated by a symbol, an inductor L32 isthe one in which an inductance produced by the coil conductor 32 isindicated by a symbol, and each of capacitors C1 and C2 is the one inwhich a capacitance occurring between the coil conductors 31 and 32 isindicated by a symbol of a lumped constant.

As described above, the two coil conductors 31 and 32 of the boosterantenna 130 are wound and arranged such that an induced current flowingthrough the coil conductor 31 and that through the coil conductor 32propagate in the same direction, and the coil conductors 31 and 32 arecoupled through the capacitances. This booster antenna has theinductances of the coil conductors themselves and the capacitancesresulting from capacitive coupling of the coil conductors, and theinductances and capacitances form a resonant circuit. It is preferablethat the resonant frequency of that resonant circuit substantiallycorrespond to the carrier frequency used in communication. This enablesan increase in the communication distance.

In FIG. 25(C), an inductor L21 is the one in which an inductanceproduced by the coil conductor of the coil antenna 100 is indicated by asymbol, and a capacitor CIC is the one in which a capacitance associatedwith the coil conductor of the coil antenna 100, such as a parasiticcapacitance of a radio-frequency integrated circuit (RFIC), is indicatedby a symbol. The inductor L21 is coupled to the inductors L31 and L32through an electromagnetic field. LC resonance occurs between theinductor L21 and the capacitor CIC. This enables the RFIC to be coupledto the LC circuit resulting from the booster antenna 130 in an impedancematched state.

FIG. 26(A) is a plan view of the antenna device 217 and FIG. 26(B) is across-sectional view of a communication terminal apparatus including theantenna device 217.

The coil antenna 100 is mounted on the main substrate (printed wiringboard) 111 in the terminal housing 320 as a surface-mount component. Thebooster antenna 130 is attached to the inner wall of the terminalhousing 320 with an adhesive layer 40 disposed therebetween.

The coil antenna 100 functions as a feed coil. The coil antenna 100 andthe booster antenna 130 are coupled through a magnetic field. Morestrictly, because a magnetic flux occurring in the planar conductor 11(magnetic flux occurring in the direction of the arrow B illustrated inFIG. 15(A)) links the coil conductors 31 and 32 of the booster antenna130, the booster antenna 130 is also coupled to the planar conductor 11through a magnetic field. That is, the three elements of the coilantenna 100, the planar conductor 11, and the booster antenna 130 arecoupled through a magnetic field. As a result, a magnetic fieldcomponent that is a loss is small, and the antenna device with a reducedloss can be achieved.

It is preferable that the direction in which the conductive pattern ofeach of the coil conductors 31 and 32 of the booster antenna 130 extendsand the direction in which the coil conductor 21 of the coil antenna 100extends be parallel to each other and that the coil conductor 21 of thecoil antenna 100 overlap the coil conductors 31 and 32 of the boosterantenna 130 in plan view. That is, it is preferable that the windingaxis of each of the coil conductors 31 and 32 of the booster antenna 130be substantially orthogonal to the winding axis of the coil antenna 100.In this case, as indicated by the broken line illustrated in FIG. 26(B),a magnetic flux links the coil conductor 21 of the coil antenna 100 andthe coil conductors 31 and 32 of the booster antenna 130. Because thecoil conductor 21 of the coil antenna 100 and a part of the coilconductors 31 and 32 of the booster antenna 130 extend in substantiallythe same direction, they are also coupled through an electric field.That is, the coil antenna 100 is directly coupled to the booster antenna130 through an electromagnetic field.

As described above, it is preferable that the antenna device(communication terminal apparatus) further include the booster antenna130. When the booster antenna 130 is arranged on a side near to theantenna at the other end in communication, the maximum distance at whichcommunication can be carried out for the antenna device can be furtherextended. When a communication signal is in the HF range, because thecoil antenna 100 and the booster antenna 130 are coupled mainly througha magnetic field, it is not necessary to use mechanical connectionmeans, such as a contact pin or a flexible cable.

The shape of the coil conductor of the booster antenna is not limited toa spiral; it may be a loop shape.

18th Embodiment

FIG. 27(A) is a plan view of an antenna device 218 according to an 18thembodiment and FIG. 27(B) is a cross-sectional view of a communicationterminal apparatus including the antenna device 218. In the antennadevice 218, the booster antenna 130 is arranged such that its coilopening is situated outside the end portion of the planar conductor 11.The other configuration is the same as that illustrated in the 17thembodiment.

Also when such a positional relationship is used, a magnetic fluxoccurring in the planar conductor 11 (magnetic flux occurring in thedirection of the arrow B illustrated in FIG. 15(A)) links the coilconductors 31 and 32 of the booster antenna 130. The direct couplingbetween the coil antenna 100 and the booster antenna 130 issubstantially the same as in the antenna device 217 in the 17thembodiment.

19th Embodiment

FIG. 28 is a plan view that illustrates a communication terminalapparatus including an antenna device 219 according to a 19th embodimentin a state where the upper housing is detached. In this example, theplanar conductor 11 is a ground conductor disposed on the main substrate111. The configuration of the coil antenna 100 is the same as thatillustrated in the first embodiment. The configuration of the boosterantenna 130 is the same as that illustrated in the 17th embodiment.

The planar conductor 11 constitutes a large proportion of the terminalhousing 320 in terms of the plane. The coil antenna 100 is arranged suchthat the coil openings are positioned along the long sides of the planarconductor. As described above, when the planar conductor 11 has theshape of a rectangle having the long sides and short sides, it ispreferable that the coil antenna 100 be arranged such that a coilopening faces a part of the long side. That is, when communication iscarried out in the state where a magnetic flux is input and output in acentral portion of the planar conductor 11, the magnetic field (magneticflux) tends to flow toward the long sides, which have a shorter distancefrom the center of the planar conductor 11. Accordingly, the arrangementin which a coil opening of the coil antenna 100 faces the long side ofthe planar conductor 11 enables more stable communication.

20th Embodiment

FIG. 29(A) is a plan view of an antenna device 220 and FIG. 29(B) is across-sectional view of the antenna device 220. The antenna device 220includes the four coil antennas 100A, 100B, 100C, and 100D. These coilantennas 100A, 100B, 100C, and 100D are mounted on the main substrate(printed wiring board) 111 in the terminal housing as a surface-mountcomponent. The booster antenna 130 can be attached to the inner wall ofthe housing, for example. The configuration of the booster antenna 130is illustrated in the 17th embodiment.

The coil antennas 100A, 100B, 100C, and 100D are disposed on therespective sides of the rectangular planar conductor 11 and arranged soas to surround the planar conductor 11. The coil conductors of the coilantennas 100A, 100B, 100C, and 100D are connected in series in adirection in which electromotive force is accumulated and connected to asingle feed circuit. The path of a magnetic flux flowing through thecoil antennas 100A, 100B, 100C, and 100D and the planar conductor 11 isthe same as that illustrated in FIG. 5(B). The connection relation amongthe coil conductors of the coil antennas 100A, 100B, 100C, and 100D isthe same as that illustrated in FIG. 5(A).

As described above, the use of the plurality of coil antennas easilyenables a necessary inductance. The arrangement in which the pluralityof coil antennas 100A, 100B, 100C, and 100D are disposed around theplanar conductor 11 strengthens the coupling between the plurality ofcoil antennas and the booster antenna 130, enhances the efficiency ofthe booster antenna 130, and reduces a loss. The advantageous effectsproduced by the use of the single planar conductor and the plurality ofcoil antennas, as illustrated in the first embodiment, are alsoobtainable.

OTHER EMBODIMENTS

The specific embodiments of the present invention are described above.The present invention is not limited to these above-describedembodiments. For example, an element other than a coil antenna, such asa semiconductor element or a chip capacitor, may be mounted. The planarconductor may be a ground electrode on a wiring substrate, oralternatively, may be a metal that sheathes a battery pack. That is, theplanar conductor is not limited to a dedicated planar conductor. Othermetal body in part (or in whole) may be used as the planar conductor inan antenna device.

The magnetic core of the coil antenna may be a ceramic body, such as aferrite ceramic body, or alternatively, may be a resin layer thatcontains ferrite powder distributed in a resin. The coil antenna, inwhich the coil conductor is wound around the surface of the magneticcore, may be overlaid with an insulating layer with the aim of, forexample, protecting the coil conductor and protecting the magnetic core.The coil conductor may be one in which metal wire is wound around themagnetic core. When the magnetic core is a ferrite ceramic, the coilconductor may be a metal sintered body, such as one made of silver,simultaneously sintered with the ferrite ceramic. In the coil antenna,in which the coil conductor is wound around the magnetic core, the coilconductor may not be formed on the top surface of the magnetic core; thecoil conductor in part or in whole may be disposed inside the magneticcore.

The antenna device in the terminal housing may be arranged in thevicinity of the front side (on the side on which a display unit and aninput operation unit are disposed) of the terminal housing, oralternatively, may be disposed above the battery pack. The coil antennamay preferably be arranged on a side adjacent to an object at the otherend in communication with respect to the planar conductor.Alternatively, the surface on which the coil antenna is arranged may beon a side opposite to an object at the other end in communication withrespect to the planar conductor. In particular, when the coil conductorincludes a portion that overlaps the planar conductor and anotherportion that does not overlap the planar conductor and also when theplanar conductor is sufficiently thin, even if the coil antenna isarranged on a side opposite to an object at the other end incommunication with respect to the planar conductor, it is sufficientlypossible for this antenna device to carry out communication with theantenna device at the other end in communication.

The antenna device may be arranged as the sub substrate in the housingin the communication terminal apparatus, or alternatively, may bearranged on the main substrate. Alternatively, the antenna device may beembedded in a card module that can be inserted into the communicationterminal apparatus. The antenna device is not limited to uses in acommunication system in the HF range. The antenna device may be used asan antenna device used in other frequency ranges, including theultrahigh frequency (UHF) range and the superhigh frequency (SHF) range,and may also be used in communication systems other than an RFID system.When the antenna device is used in an RFID system, it may be used as anantenna device in a reader/writer or may also be used as an antennadevice in an RFID tag.

The antenna device of the present invention can be used in an RFIDsystem in the HF range, for example. The communication terminalapparatus of the present invention is useful as a communication terminalapparatus that includes an RFID system in the HF range, for example.

REFERENCE SIGNS LIST

-   -   BS back surface    -   CA connection area    -   FC feed circuit    -   FE leading end    -   HP proximal portion    -   L1 to L4 coil    -   SL slit    -   W1 to W8 connection wiring    -   10 base    -   10 a, 10 b, 10 c base layer    -   11 planar conductor    -   11A first planar conductor region    -   11B second planar conductor region    -   12 a, 12 b input/output terminal    -   20 magnetic core    -   20 a, 20 c, 20 b, 20 d magnetic layer    -   21 coil conductor    -   21 a, 21 b, 21 c conductive pattern    -   21V via conductor    -   22 a, 22 b input/output-terminal connection electrode    -   23 coupling electrode    -   23 a, 23 b coupling-electrode connection electrode    -   24 coupling electrode    -   30 base sheet    -   31 first coil conductor    -   32 second coil conductor    -   40 adhesive layer    -   100 coil antenna    -   100A first coil antenna    -   100B second coil antenna    -   100C third coil antenna    -   100D fourth coil antenna    -   106 chip coil antenna    -   111 main substrate    -   112 battery pack    -   113 chip coil antenna    -   113A, 113B coil antenna    -   114 chip coil antenna    -   130 booster antenna    -   201 to 207 antenna device    -   208A, 208B antenna device    -   209A, 209B antenna device    -   210 to 220 antenna device    -   301, 310, 315, 316 communication terminal apparatus    -   320 terminal housing    -   400 coil antenna at the other end in communication

1. An antenna device comprising: a coil antenna that includes a coilconductor wound around a winding axis; a planar conductor that includesa surface and an edge end portion, the surface extending in a directionof the winding axis and the edge end portion being adjacent to a coilopening of the coil conductor; and a booster antenna that includes alooped or spiral coil conductor, the booster antenna being coupled to atleast one of the planar conductor and the coil antenna.
 2. The antennadevice according to claim 1, wherein the planar conductor is a dedicatedplanar conductor, or is part or whole of a different metal body otherthan the dedicated planar conductor.
 3. The antenna device according toclaim 1, wherein the planar conductor is a ground electrode in a wiringboard.
 4. The antenna device according to claim 1, wherein the planarconductor is an outer casing metal of a battery pack.
 5. The antennadevice according to claim 1, wherein the winding axis of the coilantenna and a winding axis of the booster antenna are orthogonal to eachother.
 6. The antenna device according to claim 1, wherein the coilconductor of the coil antenna and the coil conductor of the boosterantenna overlap each other when viewed from a plan view of the boosterantenna.
 7. The antenna device according to claim 1, wherein the planarconductor and the booster antenna overlap each other when viewed from aplan view of the booster antenna.
 8. The antenna device according toclaim 1, wherein a coil opening of the booster antenna is disposedoutside an end portion of the planar conductor when viewed from a planview of the booster antenna.